We are requesting a full-capability mass spectrometer to upgrade our analytical toxicology laboratories. This instrument will support research in two major interdisciplinary Program Grants and at least two related individual projects. The major emphasis of these programs include the chemistry of food-borne environmental toxicants, characterization of their mutagenicity and carcinogenicity, and the relationships among their metabolism, interactions with cellular macromolecules and toxicological properties. Classes of compounds under investigation include N-nitroso compounds, mycotoxins, flavanols, and food-pyrolysis products, in addition to ionizing radiation. The focus of this research has been increasingly directed toward epidemiologically-based human systems, which, typically, require analysis of low levels of large, polar, and relatively unstable compounds in complex biological matrices. Thus, we anticipate increased demand for mass spectral data from systems for which our present instruments are inadequiate. There is, however, an existing group of students and permanent research staff who are experienced in the operation these instruments, so a new mass spectrometer could be put into productive operation almost immediately.